The present invention provides a metallurgical lance which extends into a vessel for injecting solid particulate material into a vessel. Apparatus of this kind may be used for injecting metallurgical feed material into the molten bath of a smelting vessel for producing molten metal, for example by a direct smelting process.
A known direct smelting process, which relies on a molten metal layer as a reaction medium, and is generally referred to as the HIsmelt process, is described in International application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application comprises:
(a) forming a bath of molten iron and slag in a vessel;
(b) injecting into the bath:
(i) a metalliferous feed material, typically metal oxides; and
(ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metal oxides and a source of energy; and
(c) smelting metalliferous feed material to metal in the metal layer.
The term xe2x80x9csmeltingxe2x80x9d is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce liquid metal.
The HIsmelt process also comprises post-combusting reaction gases, such as CO and H2, released from the bath in the space above the bath with oxygen-containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials.
The HIsmelt process also comprises forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
In the HIsmelt process the metalliferous feed material and solid carbonaceous material is injected into the metal layer through a number of lances/tuyeres which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the smelting vessel and into the lower region of the vessel so as to deliver the solids material into the metal layer in the bottom of the vessel. The lances must withstand operating temperatures of the order of 1400xc2x0 C. within the smelting vessel. The lances must accordingly have an internal forced cooling system to operate successfully in this harsh environment and must be capable of withstanding substantial local temperature variations. The present invention enables the construction of lances which are able to operate effectively under these conditions.
According to the invention, there is provided a metallurgical lance to extend into a vessel for injecting solid particulate material into molten material held within the vessel, comprising:
a central core tube through which to pass the solid particulate material;
an annular cooling jacket surrounding the central core tube throughout a substantial part of its length, which jacket defines an inner elongate annular water flow passage disposed about the core tube, an outer elongate annular water flow passage disposed about the inner water flow passage, and an annular end passage interconnecting the inner and outer water flow passages at a forward end of the cooling jacket;
water inlet means for inlet of water into the inner annular water flow passage of the jacket at a rear end region of the jacket; and
water outlet means for outlet of water from the outer annular water flow passage at the rear end region of the jacket, whereby to provide for flow of cooling water forwardly along the inner elongate annular passage to the forward end of the jacket then through the end flow passage means and backwardly through the outer elongate annular water flow passage, wherein the annular end passage curves smoothly outwardly and backwardly from the inner elongate annular passage to the outer elongate annular passage and the effective cross-sectional area for water flow through the end passage is less than the cross-sectional flow areas of both the inner and outer elongate annular water flow passages.
Preferably, the inner and outer elongate annular passages and the end passage of the jacket are defined by
an inner tube and an outer tube interconnected at the forward end of the jacket by an annular end connector to form a single hollow annular structure which is closed at the forward end of the jacket by the annular end connector, and
an elongate tubular structure disposed within the hollow annular structure and extending within it to divide the interior of the hollow annular structure into said inner and outer elongate annular passages to a forward end part disposed adjacent the annular end connector of said hollow annular structure such that the forward end passage is defined between said forward end part of the tubular structure and the annular end connector of said single hollow annular structure.
Preferably further, the forward end part of the tubular structure is connected to the annular end connector of said hollow annular structure to set the cross-sectional flow area of the forward end passage.
Preferably further, said single hollow annular structure is mounted so as to permit relative longitudinal movement between the inner and outer tubes thereof due to differential thermal expansion or contraction thereof and the elongate tubular structure is mounted to accommodate that movement.
More specifically, it is preferred that the outer tube of the single hollow annular structure be provided with a fixed mounting means and the inner tube of that structure be supported in sliding mounting means to enable the inner tube to move axially to accommodate differential thermal expansion and contraction and the rear end of the inner tubular structure is supported in a second sliding mounting to permit the inner tubular structure to move with the inner tube of said hollow annular structure.
The inner tubular structure may be directly connected to the inner tube of the hollow annular structure to move axially with it. Such connection may be provided by a series of circumferentially spaced connectors at the rearward end of the inner tubular structure.